Resin molded articles obtained by processing a thermoplastic resin or a resin composition containing the thermoplastic resin to injection molding or the like have widely been used as industrial commodities. By the way, these resin molded articles often require high dimensional accuracy. The major cause of impairment of the dimensional accuracy is a defect phenomenon called warpage.
As a method for estimating the warpage, a method employing CAE (computer-aided engineering) which is injection molding using computer has been known. The CAE has been introduced into various resin molded article design sites and used for the purpose of shortening the resin molded article designing period and reducing a cost for making a trial product. For example, it is possible to consider a shape change such as addition of a rib, a change in molding condition such as a gate position and an injection rate, and a change of materials on a computer by setting a product shape, a molding condition, and a material physical property value and analyzing warpage.
In a designing stage before making a trial resin molded article, a method of deciding functions of a target product and a spec by performing CAE analyses under various conditions is generally employed in order to optimize the product shape, molding condition, and materials.
A method for deciding a shape and a molding condition considering the warpage is disclosed in Patent Documents 1 and 2 and so forth. The method described in Patent Document 1 includes analyzing a region which influences on warpage in a resin molded article by using a computer, wherein a shape model is divided into at least 2 regions; a parameter such as a thickness and a length is given to the desired regions; a warpage analysis is performed on each of the regions; detecting the amount of warpage sensitivity from each of the obtained amounts of warpage; and performing optimization so as to minimize the warpage.
Likewise, the method described in Patent Document 2 includes giving a plate thickness, a resin filling gate position, and a gate size as parameters and optimizing the parameters so as to minimize warpage by optimization calculation.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2004-268428
Patent Document 2: Japanese Unexamined Patent Application, Publication No. 2005-169766